fix(street-level): sequence loads, playback and nearest-photo edge cases

From gekh's review of #768, each bug with a test that fails before:

- P2: a failed sequence load clears the previous sequence's cones, resets
  the selection and can be retried; a second click while loading starts no
  second lookup. sequences.js had no tests: sequences.test.mjs now covers
  failure and retry, a superseded late answer, the cache and clearSelection.
- P2: closing a photo stops MapillaryJS sequence playback, which kept the
  hidden viewer stepping and downloading images.
- openNearest without the panel reports it instead of loading forever, and
  stops if the layer (or its provider) went off during the lookup; the
  mesh sampler's misses are bounded and forgotten with its samples; the
  sequence count is the union of ids across tiles; a provider withdraws
  only its own error, so a sequence error cannot mask KEY REJECTED; hover
  stays on (throttled) under an orbiting camera and re-picks when it
  stops; "since N days" follows the clock in a long-open tab.
- A prewarm waits for one in flight and then builds if it gave up.
- New coverage for the layer core (credits, KEY REJECTED vs REQUIRED,
  switching a provider off), the refresh wiring of the tilted-view fix and
  the draped-to-cast swap completion.
- Cleanup: loading is derived from pending; freshStreet(); tile ranking
  computes distances once and shares one path for the date line; shared
  metresBetween / whenIdle / redrawTile; one NEAREST_RADIUS_M and one
  source method list; unused contract fields, exports, getImage and the
  decoder's image branch removed; PROVIDER_COLORS lists only Mapillary.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/layers/streetLevel/selection.js

@@ -52,7 +52,6 @@ export function createSelection({ state, parts }) {
   let hoverPosition = null;
   let hoverLastPickAt = -Infinity;
   let hoverTimer = null;
-  let cameraMoving = false;
   let pointerButtons = 0;
   let removeHoverWatchers = null;
 
@@ -71,8 +70,8 @@ export function createSelection({ state, parts }) {
     const viewer = state.viewer;
     // Switched off (or torn down) since the frame was queued.
     if (!viewer || !state.enabled || !state.clickHandler) return;
-    // Orbiting, or a drag in progress: the pointer is the camera's.
-    if (cameraMoving || pointerButtons !== 0) return;
+    // A drag in progress: the pointer is the camera's.
+    if (pointerButtons !== 0) return;
     const canvas = viewer.scene?.canvas;
     if (!canvas || viewer.isDestroyed?.()) return;
     hoverLastPickAt = Date.now();
@@ -98,6 +97,11 @@ export function createSelection({ state, parts }) {
     const viewer = state.viewer;
     if (!viewer || !state.enabled) return;
     hoverPosition = movement.endPosition;
+    queueHoverPick();
+  }
+
+  /** Pick `hoverPosition` on a coming frame, within the throttle. */
+  function queueHoverPick() {
     if (hoverQueued) return;
     hoverQueued = true;
     const wait = hoverLastPickAt + HOVER_PICK_INTERVAL_MS - Date.now();
@@ -111,7 +115,12 @@ export function createSelection({ state, parts }) {
     }, wait);
   }
 
-  /** Track what makes a hover pick pointless: camera motion, held buttons. */
+  /**
+   * Track held buttons (a drag picks nothing) and camera stops. A moving
+   * camera does not stop hover: an orbiting or tracking camera never stops,
+   * and the throttle already bounds the cost. When the camera comes to rest
+   * the pointer is picked once more, since what was under it has moved.
+   */
   function watchHover(viewer) {
     const canvas = viewer.scene.canvas;
     const camera = viewer.camera;
@@ -120,16 +129,12 @@ export function createSelection({ state, parts }) {
     };
     for (const type of ['pointerdown', 'pointermove', 'pointerup'])
       canvas.addEventListener?.(type, onButtons);
-    const removeStart = camera?.moveStart?.addEventListener(() => {
-      cameraMoving = true;
-    });
     const removeEnd = camera?.moveEnd?.addEventListener(() => {
-      cameraMoving = false;
+      if (hoverPosition) queueHoverPick();
     });
     removeHoverWatchers = () => {
       for (const type of ['pointerdown', 'pointermove', 'pointerup'])
         canvas.removeEventListener?.(type, onButtons);
-      removeStart?.();
       removeEnd?.();
     };
   }
@@ -140,8 +145,8 @@ export function createSelection({ state, parts }) {
     clearTimeout(hoverTimer);
     hoverTimer = null;
     hoverQueued = false;
+    hoverPosition = null;
     hoverLastPickAt = -Infinity;
-    cameraMoving = false;
     pointerButtons = 0;
   }